1. Field of the Invention
This invention relates to a blue stretch circuit used in a TV receiver to brighten white, specifically to a blue stretch circuit with a level detection circuit which enables discerning that a level of an input signal is within a predetermined range of a reference level of a reference voltage supply using a single reference voltage supply.
2. Description of the Related Art
When white color is displayed on a TV screen, there are occasions in which the white color looks yellowish white rather than bright white. In that case, it is known that stressing blue color out of three primary colors, i.e. red (R), green (G) and blue (B), eliminates the yellowish tint and makes it bright white.
For this reason, a blue stretch circuit, which stresses blue color when it automatically detects a received color signal is white, has been bought into use. Stressing blue color can be made by increasing a gain of a B drive circuit which amplifies a blue color signal.
However, there is no simple method with conventional blue stretch circuit to detect that a received chroma signal is for white color. Another difficulty is that a level detection circuit having a simple configuration and suitable to implement in an integrated circuit is not available, while a precise level detection is required when judging the white signal with the level of the signal.